The thermodynamic efficiency of power generating cycles depends on the maximum temperature of its working fluid which, in the case for example of a gas turbine, is maximum temperature of the hot gas exiting the combustor. The maximum feasible temperature of the hot gas is limited by combustion emissions as well as by the operating temperature limit of the metal parts in contact with this hot gas, and on the ability to cool these parts below the their metal temperature limit. The cooling of the hot gas duct walls forming the hot gas flow paths of advanced heavy duty gas turbines is difficult and currently known cooling methods carry performance penalties, i.e. lead to a reduction in power and efficiency.
Cooling of combustor walls exposed to the hot combustion gases is critical to assure life time of the gas turbine. Cooling sleeves for guiding cooling gas along the walls of combustion chambers have been suggested. For example a combination of sleeves to guide the cooling gas along the combustion chamber with impingement cooling has been disclosed in the EP 13 190 131.6. For impingement cooling of a duct a sleeve is disposed a short distance away from the duct's outer surface. The impingement sleeve contains an array of holes through which compressed cooling gas discharges to generate an array of air jets which impinge on and cool the outer surface of the duct. After impingement the cooling gas flows in a cooling path delimited by the duct and the impingement sleeve towards one end of the duct. The impingement cooling has to be provided from all circumferential directions around the combustion chamber. The supply of sufficient cooling gas to feed the sleeve cooling can be difficult due to space constraints in the plenum surrounding a combustor arrangement in a gas turbine. These space constrains can lead to small cross sections in the supply channels for the sleeve cooling which in turn increase the pressure drop of the cooling arrangement. The increased pressure drop leads to corresponding high cooling gas supply pressure requirements which can be detrimental to the overall performance of the gas turbine.
The EP 2 031 302 A1 describes a combustor wall with cooling channels which integrated into the combustor wall for efficient wall cooling. After cooling the wall the cooling air is discharged into the combustion chamber.